Rotating jet nozzle with throat erosion resistant zone thickening

Abstract

The application discloses a rotary jet nozzle with an erosion-resistant area thickened throat, and belongs to the technical field of high-pressure rotary jet grouting. The nozzle body is made of tungsten carbide-cobalt hard alloy, and is provided with an inlet section, a continuous contraction section, a throat transition section and a cylindrical cluster section which are sequentially communicated, and adjacent sections are smoothly connected. The flow channel near the wall is sequentially provided with an erosion-resistant area, a radial transition area and a bearing area in the radial direction, and the mass fraction of cobalt monotonously increases from inside to outside. The erosion-resistant area is provided with a first axial strengthening area which spans the reference section of the throat, the radial thickness of the first axial strengthening area is greater than that of the adjacent second axial area, and the first axial strengthening area is connected through an axial gradual change area. The nozzle increases the thickness of the erosion-resistant area in the vicinity of the throat while maintaining the continuity of the flow channel profile, and the outer bearing area is continuously coated in the axial direction, and is used for high-pressure rotary jet grouting.

Description

Technical Field

[0001] This invention belongs to the field of high-pressure rotary jet grouting technology, specifically relating to a rotary jet nozzle with a thickened erosion-resistant throat zone. Background Technology

[0002] High-pressure jet grouting uses a high-pressure pump to deliver cement slurry and other solid-phase slurries to the nozzle. The slurry is accelerated through the nozzle's constricted flow channel, forming a high-speed jet that, in conjunction with the rotation and lifting of the drill pipe, cuts, mixes, and consolidates the formation. The nozzle's inner bore profile, throat transition, and the material composition of the slurry contact surface directly affect the flow continuity and localized erosion.

[0003] Existing rotary nozzles typically focus on improving the overall hardness of the material or employ simple conical shrinkage orifices. However, under long-term, high-speed scouring conditions with solid-phase slurries, localized material loss may still occur at the throat and its adjacent clustering section. Simply reducing the overall cobalt content in the cemented carbide will simultaneously reduce the cobalt content in the outer load-bearing region, making it difficult to separately configure the material composition of the near-wall and outer regions. Increasing the material thickness through abrupt changes in orifice diameter, internal bosses, or local steps will alter the predetermined flow channel geometry. Therefore, it is necessary to achieve a greater effective thickness of the erosion-resistant material in high-risk axial positions without disrupting the continuous flow channel, and to smoothly transition radially to the outer load-bearing material.

[0004] Public document WO2008032272A2 relates to the nozzle structure of tapered orifice and adjacent cylindrical orifice, and discloses the curved profile and the machining of hard material inner hole. Its focus is on nozzle flow channel and material machining, but does not provide a coordinated spatial configuration of axially locally thickened iso-component erosion resistant zone and radial composition gradient at the throat position.

[0005] Public document CN101818272B relates to functionally graded tungsten carbide cemented carbides with low surface binder content and high internal binder content, and discusses the problem of binder migration during liquid phase sintering. However, its general surface-internal gradient cannot directly limit the axial local thickening relationship of the present invention based on the throat.

[0006] Public document CN109161711B relates to an ultrafine-grained gradient cemented carbide with a dual gradient layer structure, which discloses the gradient configuration of different material regions. However, its "dual gradient layer" is not equivalent to the bidirectional gradient structure of the present invention, which varies along the nozzle axial position and radial distance and has the first axial reinforcement region spanning the throat reference section.

[0007] Therefore, it is necessary to make the erosion-resistant zone thicker on both sides of the throat and thinner in the adjacent axial region while keeping the flow channel free of radial steps, and to make the cobalt mass fraction gradually increase radially from near the wall to the outside. Summary of the Invention

[0008] This invention proposes a rotary nozzle with a thickened erosion-resistant throat zone. Without changing the continuous flow channel profile, the radial thickness of the erosion-resistant zone across the throat reference section is increased, and adjacent thinner regions are connected by an axial gradient zone. The cobalt mass fraction increases monotonically from the near-wall region to the outer bearing region in the radial direction, and the bearing region continuously covers the outside of the erosion-resistant zone and the radial transition zone in the axial direction.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A rotary nozzle with a thickened erosion-resistant throat zone includes a nozzle body made of tungsten carbide-cobalt hard alloy. The nozzle body is divided into an inlet section, a continuous contraction section, a throat transition section, and a cylindrical clustering section along the axial direction. The inner contours of the continuous contraction section and the throat transition section continuously contract along the flow direction. The throat transition section and the cylindrical clustering section are tangentially continuous and there is no radial step at the connection point. The interface between the two constitutes the throat reference section. The nozzle body forms an erosion-resistant zone, a radial transition zone, and a load-bearing zone that are connected radially from the inside to the outside near the flow channel. The cobalt mass fraction increases monotonically or incrementally from near the wall through the radial transition zone to the load-bearing zone. The erosion-resistant zone has a first axial reinforcement zone spanning the throat reference section and an adjacent second axial zone. The radial thickness of the erosion-resistant zone in the first axial reinforcement zone is greater than that in the second axial zone. The two are connected by an axial gradient zone where the radial thickness of the erosion-resistant zone gradually changes. The load-bearing zone continuously covers the outside of the erosion-resistant zone and the radial transition zone along the axial direction.

[0010] Preferably, the inner contours of the continuous contraction section, the throat transition section, and the cylindrical cluster section at adjacent connections satisfy tangential continuity, and the inner contour tangent of the throat transition section at the throat reference section is parallel to the nozzle central axis.

[0011] Preferably, the second axial region includes an upstream second axial region located upstream of the first axial reinforcing region and a downstream second axial region located downstream of it. The first axial reinforcing region is connected to the two second axial regions through an upstream axial transition region and a downstream axial transition region, respectively. The first axial reinforcing region has a uniform thickness section with a thickness of h1, and the two second axial regions have uniform thickness sections with a thickness of h2, where h1 / h2 is 1.5 to 3.0. The thickness of the upstream axial transition region continuously increases from h2 to h1, and the thickness of the downstream axial transition region continuously decreases from h1 to h2, where h1 is 0.65 to 1.00 mm and h2 is 0.25 to 0.50 mm.

[0012] Preferably, the first axial reinforcement zone, the upstream axial gradient zone, the downstream axial gradient zone, and the two second axial zones are all annular regions that extend continuously around the central axis of the nozzle, and the change in the radial thickness of the erosion-resistant zone along the axial direction does not change the continuous flow channel profile of the finished inner hole.

[0013] Preferably, the mass fraction cs of cobalt near the wall is 5% to 7%, the mass fraction cb of cobalt in the bearing zone is 10% to 13%, the boundary between the erosion-resistant zone and the radial transition zone is determined by the iso-composition boundary corresponding to a uniform cobalt mass fraction threshold c*, where cs<c*<cb, and the uniform cobalt mass fraction threshold c*=(cs+cb) / 2.

[0014] Preferably, the ratio of the axial length of the cylindrical bundling section to its finished inner diameter is 3 to 6.

[0015] Preferably, the arithmetic mean roughness Ra of the inner hole surface of the finished cylindrical bundling section is no more than 0.20 μm.

[0016] The continuously contracting section, the throat transition section and the cylindrical bundling section are smoothly connected, and no radial step is provided at the connection between the throat and the bundling section, so that local material reinforcement is achieved without changing the profile of the finished inner hole, and additional flow disturbance caused by geometric mutation is reduced.

[0017] The first axial reinforcement zone spans the reference cross-section of the throat, and forms a larger radial thickness of the erosion-resistant zone downstream of the throat and upstream of the bundling section; adjacent second axial zones adopt a smaller thickness and are continuously connected through the axial gradient zone, so that erosion-resistant materials can be arranged differentially according to axial positions.

[0018] Along the same axial cross-section, the mass fraction of cobalt increases from the near-wall erosion-resistant zone through the radial transition zone to the bearing zone, so that a continuous or stepwise monotonic composition transition is formed between the near-wall region and the outer bearing region, and the thickness of the erosion-resistant zone is inspected and compared on finished products through the uniform iso-composition threshold.

[0019] The radial thickness of the erosion-resistant zone is determined by the distance from the finished hole surface to the specified cobalt mass fraction boundary, the same composition threshold is used for comparison at each axial position, and the thickness variation of the material zones does not change the profile of the finished flow channel. Brief Description of the Drawings

[0020] Figure 1 is a schematic axial sectional view of a rotary jet nozzle with an erosion-resistant thickened throat according to the present invention, and the dashed box I shows Figure 2 the local amplification range.

[0021] Figure 2 is Figure 1 a partial enlarged schematic view at position I, where A-A and B-B are respectively located in the first axial reinforcement zone and the downstream second axial zone.

[0022] Figure 3 is Figure 2 a schematic cross-sectional view at positions A-A and B-B, where h1 and h2 respectively represent the radial thickness from the inner wall of the flow channel to the outer boundary of the erosion-resistant zone at the two positions.

[0023] Figure 4This is a schematic diagram illustrating the preparation and testing process of a rotary nozzle with a thickened throat erosion-resistant zone according to the present invention.

[0024] Reference numerals: 1-Nozzle body, 2-Inlet section, 3-Continuous contraction section, 4-Throat transition section, 5-Cylindrical cluster section, 6-Throat reference section, 7-Erosion resistant zone, 8-Radial transition zone, 9-Bearing zone, 10-First axial reinforcement zone. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Example

[0026] like Figure 1-4 As shown, a rotary nozzle with a thickened erosion-resistant throat zone includes a nozzle body 1 made of tungsten carbide-cobalt hard alloy. The nozzle body 1 is divided into an inlet section 2, a continuous contraction section 3, a throat transition section 4, and a cylindrical clustering section 5 along the axial direction. The inner contours of the continuous contraction section 3 and the throat transition section 4 continuously contract along the flow direction. The throat transition section 4 and the cylindrical clustering section 5 are tangentially continuous and there is no radial step at the connection. The interface between the two constitutes the throat reference section 6. The nozzle body 1 forms erosion-resistant zones that are radially connected from the inside to the outside near the flow channel. 7. Radial transition zone 8 and bearing zone 9, the cobalt mass fraction increases monotonically or incrementally from near the wall through radial transition zone 8 to bearing zone 9; the erosion-resistant zone 7 has a first axial reinforcing zone 10 spanning the throat reference section 6 and an adjacent second axial zone, the radial thickness of the erosion-resistant zone 7 of the first axial reinforcing zone 10 is greater than the radial thickness of the erosion-resistant zone 7 of the second axial zone, and the two are connected by an axial gradient zone where the radial thickness of the erosion-resistant zone 7 gradually changes; the bearing zone 9 continuously covers the outside of the erosion-resistant zone 7 and the radial transition zone 8 along the axial direction.

[0027] Preferably, the inner contours of the continuous contraction section 3, the throat transition section 4, and the cylindrical cluster section 5 at adjacent connections satisfy tangential continuity, and the inner contour tangent of the throat transition section 4 at the throat reference section 6 is parallel to the nozzle central axis.

[0028] Preferably, the second axial region includes an upstream second axial region located upstream of the first axial reinforcing region 10 and a downstream second axial region located downstream of it. The first axial reinforcing region 10 is connected to the two second axial regions through an upstream axial transition region and a downstream axial transition region, respectively. The first axial reinforcing region 10 has a uniform thickness section with a thickness of h1, and the two second axial regions have uniform thickness sections with a thickness of h2, where h1 / h2 is 1.5 to 3.0. The thickness of the upstream axial transition region continuously increases from h2 to h1, and the thickness of the downstream axial transition region continuously decreases from h1 to h2, where h1 is 0.65 to 1.00 mm and h2 is 0.25 to 0.50 mm.

[0029] Preferably, the first axial reinforcing zone 10, the upstream axial gradual change zone, the downstream axial gradual change zone and the two second axial zones are all annular zones extending continuously around the central axis of the nozzle, and the change of the radial thickness of the erosion-resistant zone 7 along the axial direction does not alter the continuous flow channel contour of the finished inner hole.

[0030] Preferably, the cobalt mass fraction cs near the wall is 5% to 7%, the cobalt mass fraction cb in the bearing zone 9 is 10% to 13%, the boundary between the erosion-resistant zone 7 and the radial transition zone 8 is determined by the isocomposition boundary corresponding to the unified cobalt mass fraction threshold c*, and cs<c*<cb, where the unified cobalt mass fraction threshold c*=(cs+cb) / 2.

[0031] Preferably, the ratio of the axial length of the cylindrical bundling section 5 to its finished inner diameter is 3 to 6.

[0032] Preferably, the arithmetic mean roughness Ra of the finished inner hole surface of the cylindrical bundling section 5 is no more than 0.20 μm. Example

[0033] As shown in Figure 1-4 , the nozzle body 1 takes the throat reference cross-section 6 as the common positioning reference for axial material configuration. Let the axial coordinate z take the throat reference cross-section 6 as the zero point, and the direction along the slurry flow direction is positive; r is the radial coordinate from the central axis; R(z) is the radius of the finished inner hole; x=r−R(z) is the radial distance extending outward from the finished hole surface. The erosion-resistant zone 7, the radial transition zone 8 and the bearing zone 9 are all determined based on the finish-machined finished hole surface. Figure 1 The position I in Figure 2 corresponds to Figure 3 , where section A—A is taken at z=4mm, and section B—B is taken at z=16 mm, both located in the cylindrical bundling section 5 with the same inner diameter. The partition lines in the diagram represent the material composition boundaries, not assembly clearances.

[0034] In terms of the continuous flow channel, let the inner diameter of the inlet section 2 be D, the total axial length of the continuous contraction section 3 and the throat transition section 4 be Lc, and the inner diameter of the cylindrical bundling section 5 be d. For −Lc≤z≤0, let s=(z+Lc) / Lc, a quintic smooth contour can be adopted: R(z)=d / 2+(D−d) / 2·(1−10s³+15s 4 −6s 5 ). The first and second derivatives of this function at s=0 and s=1 are both zero, which ensures tangent continuity and curvature continuity when the contraction contour is connected to the equal-diameter section.

[0035] In terms of axial thickness, the thickness of the erosion-resistant zone of the first axial reinforcing zone 10 is denoted as h1, and the thickness of the adjacent second axial zone is denoted as h2. The axial gradual change can adopt F(t)=3t²−2t³, 0≤t≤1; for the gradual change zone with start and end coordinates z a and zᵦ, t=(z−za ) / (zᵦ−z a ), where z a <zᵦ. In the upstream gradient zone, let h(z)=h2+(h1−h2)F(t), and in the downstream gradient zone, let h(z)=h1−(h1−h2)F(t), so that the thickness change rate at the end of the gradient zone is zero.

[0036] In terms of radial composition, let the nominal cobalt mass fraction near the wall be cs, and the nominal cobalt mass fraction of the bearing zone 9 be cb. The same nominal values of cs and cb are adopted at all axial positions of the same nozzle, with a unified threshold c* satisfying cs<c*<cb. For 0≤x≤2h(z), the target composition field can be configured according to c(z,x)=cs+(cb−cs)F[x / (2h(z))]; when c*=(cs+cb) / 2, x=h(z) corresponds to the unified isocomposition boundary, therefore 0≤x≤h(z) is defined as the erosion-resistant zone 7, h(z)<x≤2h(z) is defined as the radial transition zone 8, and x>2h(z) is the bearing zone 9.

[0037] The first axial reinforcement zone 10 increases the radial thickness of the low-cobalt material near the wall by increasing h(z), and the finished flow channel is still determined by R(z). The bearing zone 9 is continuously located outside the radial transition zone 8, and the local thickening of the erosion-resistant zone does not form a boss or radial step in the flow channel.

[0038] One design parameter combination is D=39 mm, Lc=36 mm, d=5.30 mm, and the length of the cylindrical bundling section 5 is 28 mm; h1=0.80 mm, h2=0.35 mm are selected, the first axial reinforcement zone 10 is −2≤z≤8 mm, the upstream axial gradient zone is −6 to −2 mm, and the downstream axial gradient zone is 8 to 14 mm; cs=6%, cb=12%, c*=9% are selected. Example

[0039] As Figure 4 shown, during preparation, the finished inner hole R(z), the thickness h(z) of the erosion-resistant zone, and the target cobalt mass fraction c(z,x) are first determined according to Example 2. Using the throat reference section 6 as the common axial reference, the boundaries of the upstream second axial zone, the upstream gradient zone, the first axial reinforcement zone 10, the downstream gradient zone, and the downstream second axial zone are respectively determined. The hole surface to be machined after sintering is determined according to the predetermined finishing allowance for the inner hole; each material boundary is still based on the finished hole surface and does not translate inward with the hole surface to be machined. Then, according to the axial and radial shrinkage rates measured on the sample under the same formula, same pressing and densification conditions, the axial position of the green compact and the size of each radial zone are inversely calculated respectively. When the shrinkage rate is not measured, sample calibration is performed first, and the unified shrinkage coefficient is not directly applied.

[0040] WC-Co premixed powders with cobalt mass fractions of 6% and 12% were used, and intermediate compositions of 7%, 8%, 9%, 10%, and 11% were prepared by mass. For the target cobalt mass fraction cᵢ, the mass ratio of the 12% premixed powder was (cᵢ−6%) / (12%−6%), and the remainder was 6% premixed powder. The axial regions were further segmented, and within each segment, a monotonically increasing powder composition was set from the inside out according to c(z,x). The axial gradient zone adjusted the segment radius according to the segment position, approximately corresponding to the change in h(z). The powder was sequentially loaded into each segment using a detachable outer mold, a central hole-forming core mold, and a coaxial spacer. Each segment was lightly pre-pressed to maintain its shape, and then the spacer was smoothly removed along the axial direction and the entire assembly was pressed. The segmentation and partition dimensions were selected according to the target thickness variation and forming accuracy. If significant powder mixing, voids, or segment collapse occurred after removing the spacer, the powder was reloaded.

[0041] After removing the forming agent from the compact, it undergoes pressurization and densification. Optional trial conditions include approximately 40 MPa axial compressive stress under vacuum or a protective atmosphere, and holding at 1300 ℃ for 5 min. These conditions are for process trial production; their specific applicability must be determined by examining the compaction degree, cracks, and cobalt content distribution of the compact. Samples are first prepared using the same powder and partitioning method. The axial and radial dimensions and the positions of the boundaries of each component are measured before and after densification. If shrinkage differences or cobalt migration are observed, the powder loading boundaries and densification conditions are adjusted, and the tests are repeated. Nozzles are prepared using appropriate parameters only when the finished product partitioning can maintain a cobalt content gradient from the inside out and a specified thickness relationship.

[0042] After sintering, first check the density, porosity, cracks, and radial composition distribution. Then, establish an external positioning reference and use diamond grinding combined with lapping or abrasive flow to finish the inlet section 2, continuous shrinkage section 3, throat transition section 4, and cylindrical cluster section 5. If the blank has undergone electrical discharge machining, the continuous recast layer on the surface of the finished product should be removed during subsequent finishing.

[0043] After final finishing, the flow channel profile, aperture, coaxiality, roundness, and surface roughness of the cylindrical cluster section 5 are checked. Material distribution testing involves cutting the specimen and selecting sections in the upstream second axial region, two gradient regions, the first axial reinforcement region 10, and the downstream second axial region. Metallographic observation surfaces are prepared and polished, and the cobalt mass fraction is determined radially using a compositional analysis method calibrated with a standard sample. Consistent sampling intervals and spatial averaging rules are used for each section, and instrument resolution and measurement uncertainty are recorded. Starting from the finished hole surface, boundary positions are determined by interpolation between adjacent measuring points spanning c*=9%, and h(z) is calculated. When multiple threshold intersections or significant non-monotonic distributions occur, re-measurement and checks for zone mixing, porosity, and cobalt migration are performed; intersections are not arbitrarily selected. The measured thickness and its uncertainty are compared with h1, h2, and axial position requirements; specimens that do not meet the requirements are not considered qualified finished products.

[0044] When the nozzle is installed into the matching nozzle head, the centering is completed by machining the positioning surface to ensure smooth connection between the grout delivery channel and the inlet section 2, and the matching structure is used to complete axial constraint and sealing. After completing the safety pressure bearing, sealing and cyclic load checks, it can be put into high pressure grout testing or construction use; before construction, the flow channel is cleaned and the orifice defects, plugs and tightness are checked.

[0045] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A rotary nozzle with a thickened erosion-resistant throat zone, characterized in that: Comprises a nozzle body made of tungsten carbide-cobalt hard alloy, the nozzle body is sequentially divided into an inlet section, a continuous contraction section, a throat transition section and a cylindrical bundling section along the axial direction, the inner contours of the continuous contraction section and the throat transition section continuously contract along the flow direction, the throat transition section and the cylindrical bundling section are tangent and continuous with no radial step at the connection, and the interface section of the two forms the throat reference section; the nozzle body forms an erosion-resistant zone, a radial transition zone and a bearing zone which are sequentially connected from the inside to the outside in the radial direction near the flow channel, and the mass fraction of cobalt increases monotonically or stepwise monotonically from the near-wall position through the radial transition zone to the bearing zone; the erosion-resistant zone has a first axial reinforcement zone spanning the throat reference section and an adjacent second axial zone along the axial direction, the radial thickness of the erosion-resistant zone in the first axial reinforcement zone is greater than the radial thickness of the erosion-resistant zone in the second axial zone, and the two are connected through an axial gradual change zone where the radial thickness of the erosion-resistant zone changes gradually; the bearing zone continuously covers the outer sides of the erosion-resistant zone and the radial transition zone along the axial direction.

2. The rotary nozzle with a thickened erosion-resistant throat zone according to claim 1, characterized in that: The inner contours of the adjacent connection positions of the continuous contraction section, the throat transition section and the cylindrical bundling section satisfy tangential continuity, and the tangent line of the inner contour of the throat transition section at the throat reference section is parallel to the central axis of the nozzle.

3. A rotary nozzle with a thickened erosion-resistant throat zone according to claim 1, characterized in that: The second axial zone includes an upstream second axial zone located upstream of the first axial reinforcement zone and a downstream second axial zone located downstream thereof, the first axial reinforcement zone is connected with the two second axial zones through an upstream axial gradual change zone and a downstream axial gradual change zone respectively, the first axial reinforcement zone has an equal-thickness section with a thickness of h1, the two second axial zones have equal-thickness sections with a thickness of h2, and h1 / h2 is 1.5 to 3.0; the thickness of the upstream axial gradual change zone increases continuously from h2 to h1, the thickness of the downstream axial gradual change zone decreases continuously from h1 to h2, h1 is 0.65 to 1.00 mm, and h2 is 0.25 to 0.50 mm.

4. A rotary nozzle with a thickened erosion-resistant throat zone according to claim 3, characterized in that: The first axial reinforcement zone, the upstream axial gradual change zone, the downstream axial gradual change zone and the two second axial zones are all annular zones extending continuously around the central axis of the nozzle, and the change of the radial thickness of the erosion-resistant zone along the axial direction does not change the continuous flow channel contour of the finished inner hole.

5. A rotary nozzle with a thickened erosion-resistant throat zone according to claim 1, characterized in that: The mass fraction cs of cobalt at the near-wall position is 5% to 7%, the mass fraction cb of cobalt in the bearing zone is 10% to 13%, the boundary between the erosion-resistant zone and the radial transition zone is determined by the isocomposition boundary corresponding to the unified cobalt mass fraction threshold c*, and cs<c*<cb, where the unified cobalt mass fraction threshold c*=(cs+cb) / 2.

6. A rotary nozzle with a thickened erosion-resistant throat zone according to claim 1, characterized in that: The ratio of the axial length of the cylindrical bundling section to the inner diameter of its finished product is 3 to 6.

7. A rotary nozzle with a thickened erosion-resistant throat zone according to claim 1, characterized in that: The arithmetic mean roughness Ra of the inner hole surface of the finished cylindrical bundling section is no more than 0.20 μm.

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